1. Field of the Invention
The present invention relates to touch sensitive electric switch circuits.
2. Description of the Prior Art
Touch sensitive electric switch circuits have been sold commercially, typically for use in controlling the operation of electric lights. In conventional circuits of this type an alternating current power source is connected in series with a current load, such as a light filament, and also in series with a switching element. This switching element may take the form of a triac or an SCR. Touch sensitive light switches are frequently used in association with containers for house plants, so that an individual can turn a light off and on where a touch sensitive plate for actuating the light lies in contact with the potting soil in which the plant grows. Conventional touch sensitive switch arrangements typically include a capacitive bias to the base of a transistor or to the grid of a voltage multiplying tube. A person touching a sensor plate electrically connected to a very low voltage biasing capacitor allows the small capacitor charge to disipate through his body to ground. This removes the reverse bias to allow a transistor to conduct a gating current to the triac or silicon controlled rectifier. Once the triac or silicon controlled rectifier has been gated, an open circuit condition no longer exists and current is allowed to flow from the current source through the load.